Samsung
Turn Data Roaming On or Off auf Samsung
Data roaming controls whether your Samsung phone is allowed to exchange mobile data with a carrier network that is not your own. On Android with One UI this happens automatically whenever you leave your home operator's coverage area, for example while traveling abroad or near a border region with weak home-network signal.
With Data roaming switched off, the phone still registers on the foreign network for calls and texts in most cases, but mobile internet traffic is blocked. Apps that rely on a live connection, such as maps, messengers or email, stop syncing until you reach Wi-Fi or enable the setting manually.
To change it, open Settings ➔ Connections ➔ Mobile networks and enable or disable Data roaming on the same screen.
Turning roaming on removes the block but does not remove your carrier's roaming charges. Check your plan or activate a roaming add-on before flipping the toggle if you want to avoid extra costs. If you only need occasional connectivity abroad, keeping roaming off and relying on Wi-Fi is usually the safer default.